1. Field of the Invention
This invention relates to a two-blade type impulse wrench, and more particularly to an impact pulse generating mechanism of two-blade type impulse wrench.
2. Prior Art
Recently, an impulse wrench which transduces an impact power of oil pressure to a tightening torque is often used to tighten bolts and nuts. And presently an impulse wrench which has a plurality of driving blades to generate impact pulses has been developed. But such an impulse wrench had a defect that the tightening torque per an impact pulse was small. It is due to the weakening of inertial force of rotating liner since the number of impact pulses generated in one rotation of liner increases when the number of blades is increased.
And in an impulse wrench, generally, since the output is small for its heavy weight, the motor and hydraulic pulse generator must be increased in capacity in order to obtain a hard tightening torque. Accordingly, such impulse wrench having plural blades is forced to be heavier in weight to get prescribed tightening torque, which was a serious burden for the operator.
More recently an impulse wrench which generates only one pulse per one rotation of liner, despite having two blades, has been devised (the Japanese Unexamined Utility Model Publication No. Sho. 59-140173). In this two-blade impulse wrench, two confronting linear-shaped seals formed on the inside wall of liner are deflected by several degrees from the line running through the center of a liner space, while two linear-shaped seals formed between two blades of main shaft on the symmetrical positions against the center of main shaft are deflected from the line running through the center of main shaft by the same degrees as that of the liner space.
In this two-blade type impulse wrench, however, since both of the seals formed on the inside wall of liner and on main shaft are deflected, the volumes of two high pressure compartments of four compartments which are formed when torque is generated are slightly different from each other, and the weight balance in rotation is broken due to the difference in the amount of pressure acting on the blades, which caused a rotary vibration.